Catalytically active AlCl3 -graphite intercalate

ABSTRACT

A catalytically active composition is provided that is an intercalate of graphite, aluminum halide, and a Group VA metal halide. A process for preparing an intercalate of graphite, aluminum halide, and a Group VA metal halide is also provided.

BACKGROUND OF THE INVENTION

This invention relates to intercalates of graphite and aluminumchloride. In one of its aspects this invention relates to thepreparation of intercalates of graphite and aluminum halide. In yetanother of its aspects this invention relates to the preparation ofaluminum halide-graphite intercalates also containing a Group VA metalhalide. In another of its aspects this invention relates to thepreparations of graphite and intercalates of aluminum halide usinggraphite intercalates of Group VA metal halides. In another of itsaspects this invention relates to the catalysis of alkylation reactionsusing an intercalate of graphite, aluminum halide, and a Group VA metalhalide.

This invention contemplates the ready preparation of a mixture ofaluminum halide and a Group VA metal halide intercalated in graphite. Itis well known that intercalates of aluminum halide and graphite aredifficult to prepare, with the preparation by a known method comprisingheating the aluminum halide salt with graphite in a sealed tube forseveral hours at an elevated temperature.

It is also known that intercalates of such Group VA metal halides asantimony pentachloride and graphite can be readily formed using asimilar method of heating the salt with graphite at an elevatedtemperature. The present invention combines the ready preparation of aGroup VA metal halide intercalate with graphite with an at least partialreplacement of the Group VA metal chloride by aluminum chloride. Sincethe replacement of the Group VA metal chloride is most usuallyincomplete, an intercalate of graphite, aluminum chloride, and the GroupVA metal halide results.

It is therefore an object of this invention to provide a method forpreparing a composition catalytically active for alkylation. It isanother object of this invention to provide a catalyst suitable for thealkylation of feedstocks comprising olefins and paraffins orisoparaffins. It is still another object of this invention to provide amethod for preparing intercalates of graphite, aluminum halide, and aGroup VA metal halide. It is still another object of this invention toprovide a method for preparing intercalates of graphite and aluminumhalide.

Other aspects, objects, and the various advantages of this inventionwill become apparent upon reading the specification and the attachedclaims.

STATEMENT OF THE INVENTION

According to this invention a method is provided for preparing acatalytic composition comprising contacting graphite with a Group VAmetal halide to form a first intercalate, thereafter treating the firstintercalate at a temperature sufficiently elevated and at a pressuresufficient to remove at least a part of the Group VA metal halide fromthe first intercalate composition, and thereafter contacting thecomposition from which Group VA metal halide has been removed withaluminum halide at a temperature and pressure sufficient to form asecond intercalated structure incorporating therein aluminum halide.

In one embodiment of the invention the Group VA metal halide would besufficiently removed and replaced by aluminum halide so that Group VAmetal halide would be undetectable in the intercalate composition;however, in a practical and now preferred embodiment of the invention,removal of the Group VA metal halide and replacement with aluminumhalide results in an intercalate structure of graphite, Group VA metalhalide, and aluminum halide.

In another embodiment of the invention intercalate compositions producedby the method above-described are used as catalysts in the alkylation ofolefins and paraffins or isoparaffins.

Alkylation feeds suitable for use in the alkylation reaction usingcatalysts of this invention include olefins containing from 2 to about 8carbon atoms per molecule, more preferably from 2 to 4 carbon atoms permolecule and paraffins or isoparaffins containing from 3 to about 7carbon atoms per molecule. Preferably, an isoparaffin containing from 4to 6 carbon atoms per molecule is employed. Examples of suitable olefinsinclude ethylene, propylene, butene-1, isobutylene, hexene-1, octene-1,etc. and mixtures thereof. Examples of suitable paraffins includepropane, n-butane, isobutane, n-pentane, isopentane, n-hexane,isohexane, n-heptane, isoheptane, and mixtures thereof. In a preferredreaction, isobutane is alkylated, over the catalyst compositions of thisinvention, with ethylene to produce a product having a high researchoctane number (RON), i.e., about 100, which can be used as motor fuel.

The catalyst compositions of this invention are formed in several steps.Initially, an intercalate of graphite and a Group VA metal halide isformed under conditions of time, temperature and pressure which promoteits formation. A temperature between about 80° C. and about 150° C. forbetween about 1-72 hours and a pressure from about 1-150 atmospheres canbe employed. Chlorine can be present in this operation. Examples of themetal halides include antimony pentachloride, antimony pentafluoride,bismuth pentachloride, bismuth pentafluoride, arsenic pentachloride andarsenic pentafluoride. The corresponding bromides and iodides can alsobe employed. An antimony halide, preferably antimony pentachloride, ispresently preferred.

The Group VA graphite-metal halide intercalate is subsequently treatedunder conditions of time, temperature, pressure and a purging gas orunder a vacuum which promote the removal of a portion of the Group VAmetal halide compound. A temperature ranging from about 170° to about450° C. in the presence of a purging gas such as nitrogen, argon or thelike or in a vacuum and a pressure ranging from about 0.05 to about 1atmosphere can be employed. The time to accomplish this is dependentupon the Group VA metal halide and the temperatures employed. Less timeis required at higher temperatures than lower temperatures. When themetal halide is antimony pentachloride and a progressive temperatureincrease is employed such as from about 200° to about 320° C, the timeneeded to obtain the desired results generally ranges from about 2 toabout 10 hours. After the heat treatment, the product is cooled to roomtemperature under an inert atmosphere.

The aluminum halide, whch can be the fluoride, bromide, chloride oriodide, preferably the chloride because of ready availability, is thesecond metal halide intercalated in the graphite lattice. The removal ofa portion of the Group VA metal halide is thought to facilitate theready insertion of aluminum halide in the already expanded graphitelattice. The insertion is accomplished at temperatures ranging fromabout 80° to about 120° C. by heating the components together for fromabout 5 to about 72 hours.

The molar ratio of Group VA metal halide to aluminum halide in thecompounds can range from about 1.4:1 to about 0.15:1.

The molar ratio of graphite to Group VA metal halide plus aluminumhalide in the final catalysts can range from about 2.3:1 to about 108:1.

The alkylation of isobutane with ethylene over the catalysts of thisinvention is carried out in a conventional manner at a temperature inthe range from about 70° to about 150° F (21°-66° C) and at aboutatmospheric pressure. The mole ratio of isobutane to ethylene can varyfrom about 3:1 to about 12:1, more preferably from about 5:1 to about10:1.

EXAMPLE I

An antimony pentachloride-graphite compound was prepared by reacting ina sealed bottle, 19.59 grams, 20-65 mesh (U.S. Sieve Series), graphiteobtained from Alpha Products, Beverly, Mass. and 19.22 grams of antimonypentachloride at 100° C for 48 hours. The cooled product was examined byX-ray and found to exhibit an intercalate structure. A portion of thecompound, designated control catalyst 1, was subsequently tested as analkylation catalyst. The sample was calculated to contain 50.5 weightpercent graphite and 49.5 weight percent antimony pentachloride.

Control catalyst 2 was prepared by treating a portion of controlcatalyst 1 with HF vapor at atmospheric pressure for 2 hours at roomtemperature (23° C) and then flushed with dry nitrogen for 4 hours at23° C.

Control catalyst 3 was prepared by heating in a sealed bottle, 39.13grams of the graphite used in preparing control catalyst 1 with 9.07grams of anhydrous aluminum chloride for 24 hours at 100° C. The samplewas calculated to contain 81.2 weight percent graphite and 18.8 weightpercent aluminum chloride.

Control catalyst 4 was prepared by physically mixing 20.15 grams of thegraphite with 5.39 grams anhydrous aluminum chloride. The sample wascalculated to contain 78.9 weight percent graphite and 21.1 weightpercent aluminum chloride.

Control catalyst 5 was a commercially obtained aluminumchloride-graphite intercalate described as containing 35-40 weightpercent AlCl₃, the remainder being graphite.

Control catalyst 6 was prepared by heating 60.3 grams of the graphitewith 24.3 grams anhydrous aluminum chloride and 3.2 grams antimonypentachloride in a sealed bottle at 100° C for 144 hours. Examination ofthe catalyst by X-ray disclosed that an intercalate was not formed. Thiscatalyst was not tested in alkylation.

Invention catalyst 7 was prepared by gradually heating an 8.47 gramsportion of the antimony pentachloride-graphite intercalate controlcatalyst 1 contained in a reactor under a dry nitrogen purge for 3.8hours. The product was cooled to room temperature in the nitrogenstream. The initial temperature was about 23° C and the finaltemperature reached was 300° C. Some fuming was observed as thetemperature reached 200° C. The sample lost 3.09 grams, amounting to36.5 weight percent during the heat treatment. The original intercalatewas calculated to contain 4.19 grams of antimony pentachloride (8.47grams × 49.5 weight percent SbCl₅ = 4.19 grams). The amount of SbCl₅driven off was calculated to be 3.09/4.19 × 100 or 73.7 weight percent,thus leaving 1.10 grams SbCl₅ or 21.8 weight percent of the originalsalt still present in the structure. A 5.18 grams portion of the heattreated catalyst was then reacted at 100° C in a sealed bottle with 2.87grams of anhydrous aluminum chloride for 72 hours. After 48 hours,visual examination of reactants disclosed that the aluminum chloride haddisappeared. A sample of this material was examined by X-ray and foundto exhibit the intercalate structure. The final catalyst was calculatedto contain 51.2 weight percent graphite, 35.6 weight percent aluminumchloride and 13.2 weight percent antimony pentachloride. The calculatedweight ratio of SbCl₅ :AlCl₃ was 0.37:1 corresponding to a molar ratioof 0.2:1. The calculated molar ratio of graphite to AlCl₃ + SbCl₅ in thefinal compound was 14:1.

The catalysts, except for control catalyst 6, were individuallyevaluated as alkylation catalysts in a tubular fixed bed reactor at roomtemperature (23° C). Each catalyst was charged to the reactor and agaseous feed containing 90 mole percent isobutane and 10 mole percentethylene was passed through the catalyst bed. The effluent was analyzedby means of gas-liquid chromatography. The gaseous space velocities ofthe feed (volumes feed per volume catalyst per hour, GHSV) used in eachrun, the ethylene conversion obtained and selectivity to C₆ arepresented in the following table.

                                      TABLE                                       __________________________________________________________________________    Alkylation With Graphite-Metal Chloride Catalysts                             Catalyst                                                                      Run                                                                              Cat.                                                                             Wt. %      Reaction                                                                            Feed Ethylene                                                                              Select-                                   No.                                                                              No.                                                                              AlCl.sub.3                                                                        SbCl.sub.5                                                                        g  Time, Hrs.                                                                          GHSV Conversion, %                                                                         ivity.sup.2                               __________________________________________________________________________    1  1  na.sup.1                                                                          49.5                                                                              3.02                                                                             1     5354 1.7     nd.sup.3                                  2  2  na  49.5                                                                              2.88                                                                             0.2   6287 0       0                                         3  3  18.8                                                                              na  6.21                                                                             1.8   52   26      96                                        4  4  21.1                                                                              na  7.45                                                                             1.5   58   50      90                                        5  5  35.40                                                                             na  3.69                                                                             1.8   194  100     66                                        6  7  35.6                                                                              13.2                                                                              2.32                                                                             2     3785 100     92                                        __________________________________________________________________________     Notes:                                                                        .sup.1 Not applicable                                                         .sup.2 Selectivity to C.sub.6                                                 .sup.3 Not determined                                                    

Runs 1 and 2 show that a SbCl₅ -graphite intercalate possesses onlysmall catalytic activity for the alkylation of ethylene and isobutane atroom temperature. Run 3 shows that an aluminum chloride-graphitecompound made according to the procedures generally used in theinvention is only moderately active as a catalyst under the conditionsused. Run 4, made with a deliberate admixture of graphite and aluminumchloride exhibits moderate activity and the results obtained suggestthat the run 3 catalyst is also a physical mixture. Aluminum chloride iswell known as an alkylation catalyst but it does not have the capacityby itself to effect 100% conversion of ethylene and isobutane at roomtemperature to a C₆ product as runs 3 and 4 show. Run 5 demonstrates,however, that a graphite-aluminum chloride intercalate is active at roomtemperatures as an alkylation catalyst for the reaction of ethylene andisobutane. Invention run 6 shows that an intercalate composed ofgraphite-SbCl₅ -AlCl₃ prepared according to the invention is much moreactive as an alkylation catalyst at room temperature than the otherAlCl₃ -graphite catalysts (100% conversion at almost 20 times the spacevelocity) in addition to showing a higher selectivity (26 pointshigher). Invention catalyst 7 is used in run 6.

The intercalate compounds of this invention are readily formed undermild conditions and they possess utility for alkylation under mildreaction conditions.

We claim:
 1. A method for preparing an intercalate compositioncomprising graphite and aluminum halide comprising:(1) contactinggraphite with a Group VA metal halide at a temperature below thedecomposition temperature of the Group V halide and pressure sufficientand for a time sufficient to form a first intercalate composition, (2)treating said first intercalate composition at a temperaturesufficiently elevated and at a pressure sufficient to remove at least aportion of Group VA metal halide from the first intercalate composition,and (3) contacting said intercalate composition from which Group VAmetal halide has been at least partially removed with aluminum halide ata temperature below the decomposition temperature of the aluminum halideand pressure sufficient to form a second intercalated structurecomprising aluminum halide, graphite, and a Group VA metal halidepresent in a molar ratio of Group VA metal halide to aluminum halide ofabout 1.4:1 to 0:1.
 2. A method of claim 1 wherein said firstintercalate is treated in the presence of a flow of an inert gas toremove Group VA metal halide.
 3. A method of claim 1 wherein thetemperature of graphite and Group VA metal halide during contacting isin the range of about 80° C to about 150° C; the temperature for removalof Group VA metal halide is in the range of about 170° C to about 450°C; and the temperature for contacting of aluminum halide is in the rangeof about 80° C to about 120° C.
 4. A method of claim 1 wherein saidGroup VA metal halide is incompletely removed so that the compositionresulting from contact with aluminum halide is an intercalated structureof grahite, Group VA metal halide, and aluminum halide.
 5. A method ofclaim 1 wherein said Group VA metal halide is an antimony chloride andsaid aluminum halide is aluminum chloride.
 6. A composition of mattercomprising an intercalated structure of graphite, aluminum halide andGroup VA metal halide present in a molar ratio of Group VA metal halideto aluminum halide of about 1.4:1 to 0:1.
 7. A composition of claim 6wherein the molar ratio of graphite to Group VA metal halide plusaluminum halide ranges from about 2.3:1 to about 108:1.
 8. A compositionof claim 6 wherein the Group VA metal is antimony and all halides arechloride.
 9. A method of claim 1 wherein all the Group VA metal halideis removed in step (2) so that the resulting composition is anintercalated structure of graphite and aluminum halide.